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Phys 335 > Final Exam GI > Flashcards

Final Exam GI Flashcards

1
Q

GI Functions in homeostasis (6)

A
  • intake of nutrients, ions, water
  • digestion
  • absorption into body
  • detox foreign substances
  • excretion of waste products
  • immune function
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2
Q

blood in GI system empties into _____ which goes through _____ .

A

portal vein, the liver

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3
Q

Name of veins that come out of the liver and empty into the vena cava

A
  • hepatic veins
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4
Q

Basic processes of the GI tract

A
  • motility
  • secretion
  • digestion
  • absorption
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5
Q

what colors feces brown?

A

bilirubin (breakdown of old RBC in liver)

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6
Q

3 main nutrients

A
  • Carbohydrates
  • Proteins
  • Fats
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7
Q

absorbable units of the three main nutrients

A
  • carbohydrates –> monosaccharides
  • proteins –> amino acids
  • fats –> monoglyceride/ fatty acids
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8
Q

path of digestion (organs)

A

esophagus, stomach, small intestine, large intestine, rectum

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9
Q

sphincters

A
  1. upper esophageal sphincter
  2. lower esophageal sphincter
  3. pyloric sphincter
  4. sphincter of oddi
  5. ileocecal valve
  6. internal anal sphincter
  7. external anal sphincter
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10
Q

which sphincter is called the “cardiac sphincter”?

A
  • lower esophageal sphincter

- can have acid splash up into esophagus, causes heart burn

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11
Q

Sphincter of oddi function

A
  • pancreatic ducts converge and exocrine secretions from liver and gallbladder secrete from here
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12
Q

which sphincters are skeletal muscle?

A

1 & 7 (upper esophageal sphincter and external anal sphincter)

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13
Q

4 major parts of the gut wall (lumen to abdominal cavity)

A
  • mucosa, submucosa, muscularis externa, serosa
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14
Q

Mucosa

A
  • very convoluted
  • have mucus cells and endocrine cells in single layer of epithelium
  • epithelium, lamina propria, muscularis mucosa
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15
Q

Lamina Propria

A
  • in mucosa layer

- has lots of capillaries, neurons

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16
Q

plexus layers have ______

A

-neurons

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17
Q

function of serosa

A
  • reduce friction
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18
Q

Submucosal plexus regulates _____

A

secretion

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19
Q

Circular muscle regulates ______

A

-narrowing (helps to mix)

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20
Q

Myenteric plexus regulates ______

A
  • motility
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21
Q

Longitudinal Muscle regulates ______

A
  • shortening, propulsive movement, mixing
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22
Q

Important GI hormones (4)

A
  • Gastrin
  • Cholecystokinin (CCK)
  • Secretin
  • Glucose-dependent insulinotropic peptide (GIP)
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23
Q

Enteric Nervous System (2 nerve plexus names also)

A
  • Intrinsic neural control, short reflexes
  • submucosal nerve plexus, and myenteric nerve plexus
  • coordinates processes
  • more neurons than in spinal cord
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24
Q

Central Nervous system role in GI

A
  • has extrinsic neural control, long reflexes
  • parasymp NS activates
  • sympathetic NS inhibits
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25
Q

look at page 131

A

regulation of basic processes graph

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26
Q

three phases of GI control

A
  • cephalic
  • gastric
  • intestinal
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27
Q

Cephalic Phase

A
  • stimuli in your head, feed-forward
  • stimulated by: thought, sight, smell, taste,
  • response to these stimuli: increased excitatory parasymp outflow (salivary secretion, motility)
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28
Q

Gastric Phase

A
  • initiated when food is in the stomach
  • stimulated by: stretch, acidity, amino acids, peptides
  • responses to these stimuli: short and long loop reflexes, gastrin
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29
Q

Intestinal Phase

A
  • initiated when food is in the small intestine
  • stimulated by: stretch, acidity, osmolarity, digestive products
  • response to these stimuli: short and long loop reflexes, secretin, CCK, and GIP (these are secreted from intestine)
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30
Q

Mouth/Pharynx/Esophagus Motility

A
  • Mastication (chewing)

- Deglutition (swallowing)

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31
Q

Mouth/Pharynx/Esophagus Motility: Mastication

A
  • grinds, increases surface area, mixes with saliva (into bolus), allows chemoreception
  • voluntary (skeletal muscle), but with complex organization of movements
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32
Q

Mouth/Pharynx/Esophagus Motility: Deglutition

A
  • oropharyngeal phase

- esophageal phase

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33
Q

Mouth/Pharynx/Esophagus Deglutition (swallowing)– Oropharyngeal phase

A
  • whole process is organized by a medulla oblongata
  • begins with voluntary closing of lips and elevation of tongue, become irreversible reflex when bolus hits back of oral cavity
  • upper esophageal sphincter closes rapidly
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34
Q

function of uvula

A
  • blocks off nasal passages

- part of soft palate

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35
Q

why does upper esophageal sphincter close rapidly?

A
  • prevent eventual eructation (burping), borborygmi (grumbling stomach), and flatulation
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36
Q

how much do we flatulate a day?

A

0.5-1.5L /day

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37
Q

eructation

A

burping

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38
Q

borborygmi

A

grumbling stomach

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39
Q

Mouth/Pharynx/Esophagus Deglutition– esophageal phase

A
  • upper 1/3 of esophagus is skeletal muscle, then all smooth muscle
  • peristaltic wave organized by brainstem
  • local stretch activates secondary peristaltic wave
  • LES sphincter relaxes and bolus enters stomach
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40
Q

weak LES

A
  • caues acid reflux, causes “heartburn”
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41
Q

rebound contraction

A
  • closing UES
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42
Q

when does peristalsis stop?

A
  • when bolus clears esophagus
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43
Q

Mouth/Pharynx/Esophagus - Secretions

A
  1. Saliva

2. Mucus

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44
Q

Mouth/Pharynx/Esophagus- Secretions.. Saliva

A
  • activated in feed-forward and feed-back mode during cephalic phase
  • moistens and lubricates food
  • initiates small amount of digestion of polysaccharides by salivary amylase
  • dissolves small amt of food
  • kills bacteria (lysozyme)
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45
Q

Symp stimulation.. saliva is ______

A

sticky

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46
Q

Parasymp stimulation.. saliva is _____

A

watery

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47
Q

Xerostomia

A
  • no saliva produced

- have difficulty chewing, speaking, swallowing, halitosis, and tooth decay

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48
Q

Halitosis

A
  • bad breath (acetone breath)
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49
Q

Mouth/Pharynx/Esophagus Secretions… Mucus

A
  • what esophagus secretes
  • secreted throughout entire GI tract
  • forms slippery, protective surface, buffers pH
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50
Q

Mouth/Pharynx/Esophagus Digestion

A

Minor digestion of carbs (amylase)

51
Q

Mouth/Pharynx/Esophagus Absorption

A
  • virtually no foods, some drugs like nitroglycerine
52
Q

Nitroglycerine function

A
  • absorbed into bloodstream through mouth
  • forms Nitric Oxide
  • dilates arterioles
53
Q

Parts of Stomach

A
  • upper esphogeal sphincter
  • Body (upper half)
  • Fundus (very upper part of stomach)
  • Antrum (lower half)
  • Pyloric sphincter
54
Q

What does the body of the stomach secrete

A
  • mucus, pepsinogen, HCl
55
Q

What does the antrum secrete

A
  • mucus, pepsinogen, and gastrin
56
Q

secretion from stomach occurs where?

A
  • gastric pits/glands
57
Q

gastric pits/glands go down into what layer of the gut wall?

A
  • mucosa, lamina propria
58
Q

Chyme is what?

A
  • gastric juice + food
59
Q

what do parietal cells secrete?

A
  • HCl
60
Q

what do ECL cells secrete?

A
  • histamine paracrine agent
61
Q

What do chief cells secrete?

A
  • pepsinogen
62
Q

what do mucous cells secrete?

A
  • mucus, bicarb
63
Q

HCO3 and mucus form _____ which is ____ thick

why?

A
  • gastric mucosal layer… 0.2mm thick

- buffer the pH, keep pH of 7 near epithelial cells

64
Q

HCl secretion from parietal cell mechanism

A
  • see page 138
65
Q

Volume of HCl secreted in one day?

A

2 L

66
Q

Stomach: signals that stimulate/inhibit HCl secretion & general mech

A
  • stimulate: gastrin, histamine, ACh
  • inhibit: somatostatin
  • same mech to put in transporters as aquaporins in collecting duct
67
Q

Enterogastric reflex

A
  • intestine signals stomach to stop producing HCl when chyme enters Small Intestine
  • enzymes in S.I. cannot function at low pH
68
Q

High HCl secretions act on _____ and ____

why?

A

Somatostatin (+), and Gastrin (-) to stop own secretion

69
Q

Secretion of Pepsinogen

A
  • pepsinogen secreted from chief cells as a zymogen
  • HCl cleaves to make Pepsin, which can then make more pepsin by cleaving pepsinogens (autocatalytic)
  • pepsin breaks down proteins
70
Q

What type of enzyme is pepsin?

A
  • protease
71
Q

How much total digestion of proteins is completed by pepsin?

A
  • 20%
72
Q

When HCl activates pepsinogen, what else branches off the HCl arrow?

A
  • intrinsic factor (secreted also by Parietal cells)
73
Q

What is intrinsic factor?

A
  • protein that binds and facilitates absorption of B12 into ileum
  • whole complex is endocytosed
  • see page 140
74
Q

Why is B12 important?

A
  • helps to make RBCs

- only gastric function ESSENTIAL for life!

75
Q

What is absence of B12 called?

A
  • Pernicious Anemia

- “sneaky”

76
Q

Stomach: Motility (3 stages)

A
  • Receptive Relaxation
  • Peristaltic Waves
  • Gastric Emptying
77
Q

Stomach: Motility - Receptive Relaxation

A
  • starts during cephalic phase
  • parasymp acts on enteric nerve plexus, secrete Serotonin and NO
  • increase of stomach volume from 50ml to 1.5L
78
Q

Why does stomach feel funny after taking SSRIs?

A
  • most serotonin is working at the level of the GI tract

- blocking serotonin reuptake affects the stomach

79
Q

Stomach: Motility - Peristaltic Waves

A
  • waves of smooth muscle contractions
  • mix and propel food
  • pyloric sphincter only allows small amount of chyme into s.i. after each wave, rest gets retropulsed
80
Q

Stomach body smooth muscle vs antrum smooth muscle

A
  • Body= thin

- Antrum = thick

81
Q

BER

A
  • basic electrical rhythms
  • slow waves
  • contraction strength increases with amt of time spent above threshold
82
Q

Frequency of BER

A
  • 3-5/min in stomach

- doesn’t increase with amount of food you eat

83
Q

What type of cells control BER?

A
  • Interstital cells of Cajal (ICC)

- “pacemakers of gut”

84
Q

Stomach: Motility - Gastric Emptying

A
  • stimulated by stomach distension, chyme fluidity, gastrin
  • increased tone of fundus and body
  • increased strength of peristaltic waves
  • inhibition of contraction in S.I.
85
Q

Same things that increase/decrease ______, increase/decrease _____

A

acid secretion, stomach motility

86
Q

How long does Gastric Emptying take & why is this beneficial?

A
  • 2-4 hours

- need time to absorb nutrients, want to slowly move food into S.I. to allow adequate time

87
Q

Stomach: Digestion

A
  • Physical grinding

- proteins –> peptides

88
Q

Stomach: Absorption

A
  • aspirin (and other weak acids)

- Alcohol (much slower than S.I.)

89
Q

Small Intestine Anatomy

A
  • ~9 feet long
  • duodenum (~1 ft)
  • jejunum (~1 ft)
  • ileum (~7 feet)
    ileocecal sphincter
90
Q

Where does most of the absorption occur in the small intestine?

A
  • duodenum and jejunum
91
Q

Can you live without your small intestine?

A
  • NO
92
Q

Small Intestine: Secretion

A
  • Water, mucus, bicarb, high Na, high Cl
93
Q

Why is there high Na and Cl secretion in the S.I.?

A
  • essential for secondary active transport processes that absorb glucose and AA
94
Q

Importance of the pancreas

A
  • secretes enzymes essential for digestion

- secretes bicarb

95
Q

General enzymes the pancreas secretes and what cells secrete them

A
  • amylase
  • proteases
  • lipases
  • from exocrine acinar cells
96
Q

what cells in pancreas secrete bicarb and why?

A
  • duct cells.. to neutralize acid
97
Q

how are secretions from liver and pancreas delivered to S.I.?

A
  • sphincter of oddi
98
Q

See page 146 for regulations

A

look

99
Q

Liver contributions to secretions

A
  • bile
100
Q

What is bile made of? (6 things)

A
  • bicarb (neutralize acid)
  • phospholipids (emulsify fats)
  • bile salts (emulsify fats)
  • cholesterol (excreted)
  • bile pigments (bilirubin) (excreted)
  • organic waste (excreted)
101
Q

Pathway from fat globule to chylomicron (5)

A
  • fat globule
  • emulsion droplets
  • micelles
  • molecs of fatty acids & monoglycerides
  • chylomicrons
102
Q

point of emulsification

A
  • increase surface area

- lipase can break down fats into micelles

103
Q

What happens to micelles?

A
  • interact with the bile salts and phospholipids more to make fatty acids and monoglycerides
  • can get through membrane and sent to E.R.
104
Q

chylomicrons are _____ that enter into the _____ system

A

lipoproteins , lymphatic

105
Q

what happens to most bile salts?

A
  • reabsorbed at the ileum (95%)

- other 5% lost in feces

106
Q

circulation that brings 95% of bile salts back to liver?

A
  • enterohepatic circulation
107
Q

Bile salts and phospholipids are ______ (nonpolar/polar)

A

-BOTH (amphipathic)

108
Q

CCK stimulates:

A
  • enzyme secretion from pancreas
  • gallbaldder contraction to deliver more bile
  • sphincter of oddi relaxation
109
Q

Small Intestine: Digestion

A
  • pancreatic and membrane-bound enzymes do all of the body’s digesting of macroscopic fuel molecs into absorbable units
110
Q

How is trypsinogen activated?

A
  • membrane-bound enterokinase converts to trypsin

- trypsin can then activate other zymogens in the S.I.

111
Q

Carbohydrate Digestion

A
  • pancreatic amylase and brush border enzymes convert polysaccharides to monosaccharides
112
Q

Protein Digestion

A
  • proteins converted to amino acids by proteases

- small peptides then converted to AA by brush border peptidases

113
Q

S.I. absorption

A
  • HUGE AMOUNT

- water, monosaccharides, AA, FA, ions, vitamins, iron, dead GI cells

114
Q

How many dead GI cells are absorbed / day

A
  • 17 billion
115
Q

whole inner lining of GI tract is replaced every _____ days

A
  • 4-5
116
Q

what allows for large surface area in S.I. for absorption?

A
  • long length, highly folded, villi, and microvilli

- total surface area same as lungs, like a tennis court

117
Q

Another name for microvilli?

A
  • brush border
118
Q

S.I. Absorption mechanisms

A
  • like renal absorption
  • intestinal capillaries collect into hepatic portal vein which goes to liver
  • triglyc and fat-soluble vitamins are absorbed into lacteal of lymphatic system
119
Q

S.I. Motility (2 parts)

A
  • Segmentation during a meal

- Migrating Myoelectric complex after a meal

120
Q

S.I. Motility: Segmentation

A
  • not peristalsis
  • stationary contractions (v. small/slow net movement)
  • alternating areas of contraction and relaxation
  • BER in circular smooth muscle
121
Q

BER frequency in S.I. (duodenum vs ileum)

A
  • 12/min in duodenum

- 9/min in ileum

122
Q

what causes BER depolarizations in S.I.?

A
  • excitatory NTs and hormones
123
Q

S.I. Motility: MMC after a meal

A
  • peristalsis
  • “intestinal housekeeper”
  • organized peristaltic contractions after a meal has been digested and absorbed
  • contractions “sweep” a few feet adn then die out
  • contents swept into colon
124
Q

What hormone causes intestinal housekeeper?

A
  • motilin (secreted by S.I. cells) during fasting

Phys 335 (3 decks)

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